assembly - MIPS Exception Printing NOT working -

mips exception handler code not working: in following code attempt print out addresses of instruction caused exception (register $14) , type of exception (register $13). have exhausted every possible route think of.

the error message gives:

"lw": few or incorrectly formatted operands. expected: lw $t1,-100($t2)

thank you!

  mfc0 $k0,$14 # coprocessor 0 register $14 has address of trapping instruction      lw $a0, $k0 # address of string print      li $v0, 4 # print string service      syscall      mfc0 $k0,$13 # coprocessor 0 register $13 has type of exception      lw $a0, $k0 # address of string print      li $v0, 4 # print string service      syscall 

instead of:

lw <regdst>,<regsrc> 

do:

move <regdst>,<regsrc> 

move pseudo-op [most likely] generate:

addu <regdst>,<regsrc>,$zero 

or, done with:

addiu <regdst>,<regsrc>,0 

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side note: i've written full exception handler before, sure first instruction [more or less]:

move $k0,$at 

and, epilog looks like:

move $at,$k0 eret 

i establish stack frame normal function [saving other registers changed] , pop @ end

the reason mention this, exception handler must save every register change , restore original value on exit if it's going return base code (e.g. might trap , fix overflow exception).

this [especially] true handling breakpoints.